[tor-commits] [tor/release-0.4.4] Revert "config: Make clients tell dual-stack exits they prefer IPv6"

[nickm at torproject.org]

commit 66d5292ee6a173b21e5a54a669e8e584c6781e3a
Author: David Goulet <dgoulet at torproject.org>
Date:   Tue Jul 7 12:05:27 2020 -0400

    Revert "config: Make clients tell dual-stack exits they prefer IPv6"
    
    This reverts commit bf2a399fc0d90df76e091fa3259f7c1b8fb87781.
    
    Don't set by default the prefer IPv6 feature on client ports because it breaks
    the torsocks use case. The SOCKS resolve command is lacking a mechanism to ask
    for a specific address family (v4 or v6) thus prioritizing IPv6 when an IPv4
    address is asked on the resolve SOCKS interface resulting in a failure.
    
    Tor Browser explicitly set PreferIPv6 so this should not affect the majority
    of our users.
    
    Closes #33796
    
    Signed-off-by: David Goulet <dgoulet at torproject.org>
---
 changes/ticket33796     |  7 +++++++
 doc/tor.1.txt           | 16 +++++++---------
 src/app/config/config.c |  2 +-
 src/test/test_config.c  |  2 --
 4 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/changes/ticket33796 b/changes/ticket33796
new file mode 100644
index 000000000..9a98bf2d9
--- /dev/null
+++ b/changes/ticket33796
@@ -0,0 +1,7 @@
+  o Removed features (IPv6, revert):
+    - Revert the client port prefer IPv6 feature because it breaks the
+      torsocks use case. The SOCKS resolve command is lacking a mechanism to
+      ask for a specific address family (v4 or v6) thus prioritizing IPv6 when
+      an IPv4 address is asked on the resolve SOCKS interface resulting in a
+      failure. Tor Browser explicitly set PreferIPv6 so this should not affect
+      the majority of our users. Closes ticket 33796; bugfix on 0.4.4.1-alpha.
diff --git a/doc/tor.1.txt b/doc/tor.1.txt
index 7b3150e2a..9d073635a 100644
--- a/doc/tor.1.txt
+++ b/doc/tor.1.txt
@@ -1492,16 +1492,14 @@ The following options are useful only for clients (that is, if
     Other recognized __flags__ for a SocksPort are:
     **NoIPv4Traffic**;;
         Tell exits to not connect to IPv4 addresses in response to SOCKS
-        requests on this connection. (Allowing IPv4 is the default.)
-    **NoIPv6Traffic**;;
-        Tell exits to not connect to IPv6 addresses in response to SOCKS
-        requests on this connection. This option is only relevant when SOCKS5
-        is in use, because SOCKS4 can't handle IPv6.  (Allowing IPv6 is the
-        default.)
-    **NoPreferIPv6**;;
+        requests on this connection.
+    **IPv6Traffic**;;
+        Tell exits to allow IPv6 addresses in response to SOCKS requests on
+        this connection, so long as SOCKS5 is in use.  (SOCKS4 can't handle
+        IPv6.)
+    **PreferIPv6**;;
         Tells exits that, if a host has both an IPv4 and an IPv6 address,
-        we would prefer to connect to it via IPv4. (IPv6 is the default in
-        recent versions of Tor.)
+        we would prefer to connect to it via IPv6. (IPv4 is the default.)
     **NoDNSRequest**;;
         Do not ask exits to resolve DNS addresses in SOCKS5 requests. Tor will
         connect to IPv4 addresses, IPv6 addresses (if IPv6Traffic is set) and
diff --git a/src/app/config/config.c b/src/app/config/config.c
index 71f8c18ca..ba2cecd9a 100644
--- a/src/app/config/config.c
+++ b/src/app/config/config.c
@@ -5610,7 +5610,7 @@ port_cfg_new(size_t namelen)
   /* entry_cfg flags */
   cfg->entry_cfg.ipv4_traffic = 1;
   cfg->entry_cfg.ipv6_traffic = 1;
-  cfg->entry_cfg.prefer_ipv6 = 1;
+  cfg->entry_cfg.prefer_ipv6 = 0;
   cfg->entry_cfg.dns_request = 1;
   cfg->entry_cfg.onion_traffic = 1;
   cfg->entry_cfg.prefer_ipv6_virtaddr = 1;
diff --git a/src/test/test_config.c b/src/test/test_config.c
index 095eb24c4..cb0d9bba2 100644
--- a/src/test/test_config.c
+++ b/src/test/test_config.c
@@ -4160,8 +4160,6 @@ test_config_parse_port_config__ports__ports_given(void *data)
   /* Test entry port defaults as initialised in port_parse_config */
   tt_int_op(port_cfg->entry_cfg.dns_request, OP_EQ, 1);
   tt_int_op(port_cfg->entry_cfg.ipv4_traffic, OP_EQ, 1);
-  tt_int_op(port_cfg->entry_cfg.ipv6_traffic, OP_EQ, 1);
-  tt_int_op(port_cfg->entry_cfg.prefer_ipv6, OP_EQ, 1);
   tt_int_op(port_cfg->entry_cfg.onion_traffic, OP_EQ, 1);
   tt_int_op(port_cfg->entry_cfg.cache_ipv4_answers, OP_EQ, 0);
   tt_int_op(port_cfg->entry_cfg.prefer_ipv6_virtaddr, OP_EQ, 1);